LeetCode 48. Rotate Image

Problem:

You are given an n x n 2D matrix representing an image.

Rotate the image by 90 degrees (clockwise).

Note:

You have to rotate the image in-place, which means you have to modify the input 2D matrix directly. DO NOT allocate another 2D matrix and do the rotation.

 

Example 1:

Given input matrix =

[ [1,2,3],

[4,5,6],

[7,8,9] ],

 

rotate the input matrix in-place such that it becomes:

[ [7,4,1],

[8,5,2],

[9,6,3] ]

 

Example 2:

Given input matrix =

[ [ 5, 1, 9,11],

[ 2, 4, 8,10],

[13, 3, 6, 7],

[15,14,12,16] ],

 

rotate the input matrix in-place such that it becomes:

[ [15,13, 2, 5],

[14, 3, 4, 1],

[12, 6, 8, 9],

[16, 7,10,11] ]

 

-Summary-

1. Reverse the matrix first

2. Transpose the matrix to move around the elements. The element will be rotated with 90 degrees. (Clockwise)

 

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